CoolingDiscuss all of the aspects of cooling that you can think of! Radiators, transmissions, electric fans, etc.
Welcome to ThirdGen.org!
Welcome to ThirdGen.org.
You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, at no cost, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, join the ThirdGen.org community today!
Ok, beleive me, i've read many threads on this issue.. to be honest I just get confused with all the different answers. So.. What I am trying to figure out is where my fan switch is located. I own an 88 firebird with a 305 TBI code E, Single fan setup..
Now alot of people are stating that the switch is located on the passenger side head.. I however can only find a switch on the driver side head between the plugs.. could this be the switch I am looking for? If not, could anyone explain what this switch on the drivers side is?
Your responses with be greatly appreciated, thank you.
Oh and I might as well throw this in here too.. Im ordering a 160 degree fan switch..you dont really think that is considered to be running too cold do you? cooler the better right? wrong?
Drivers side is the coolant guage sender. I believe (but don't quote me) that single fans are controlled by the computer. You can wire a switch in though. I believe the threads are still in the head even if there's something not filling them. Between 6 & 8 sparkplugs.
w/ my single fan setup I am using a 180 thermostat & fan switch 200 on & 185 off (thats the switch located near starter. there another temp switch located near 1 & 3 plug wires if I remember. gas milage used to be better until I switched to lower temp but w/ 1 fan will keep at 180 degrees. if I go 2 fans then I'll go back to 190 for improved milage
not sure what function of 2nd temp switch by 1 & 3 wires is but its there.
There is no "switch" in the driver's side head. Only a sensor.
The temp gauge sensor is in the driver's side head between the #1 & #3 spark plugs.
The fan switch (NOT sensor) is in the EXACT SAME HOLE in the pass side head; between the #6 & #8 spark plugs.
I would think 160° would be "too cold". Since your thermostat is a MUCH higher temp than that, the fan will be running basically 100% of the time, even when it's silly to waste engine power on it. Like cruising down the freeway or something.
The original fan switch turns the fan on at about 235°. In other words, in the factory's opinion, the engine DOES NOT NEED COOLING AT ALL until it reaches this temp. Now granted, they're just the factory, so you wouldn't expect them to know anything about their cars, or anything like that; but it's something to think about before doing something goofy like that.
__________________ Numquam ponenda est pluralitas sine necessitate. — William of Ockham, from Quaestiones et decisiones in quattuor libros Sententiarum Petri Lombardi
Roughly paraphrased into modern English, and applied to figuring out what's wrong with your car:
The simplest explanation that fits all the facts is probably the right one.
Appreciate clearing up info, that's what I look for/need. hey, I'd go for the factor 235 design/setting but sometimes, even with the lower 200/185 temp switch, the fan never kicks in. Last night was one of those times (250+ no fan B4 with a new 235 switch installed on pass side, the fan never kicked in unless a/c was on, ok maybe twice but there were plenty times when were in 250's & no fan. so maybe you can see why I'm using a lower temp switch that works 95% of the time... those double fans reallly sound good at this point lol. I replaced the sensor on driver's side B4 , but no change to fan control. What does the sensor on the drivers side feed?
Thank you douchermann for clearing that up for me. I did a test and it is indeed the temp sensor for my temp gauge. I forgot to mention that I installed a 160 degree thermostat, which is why I ordered the switch to go along with it. from my undertstanding the factory setting of 195 degrees were set in place for emmission reasons, such as burning off the access fuel or fumes that the engine does not fire up.I could be way off, but I figured this meant the engine simply will not need the access fuel for power so lets run the engine so hot it will just burn away. therefore I figured, for the sake of the life of my engine and performance, it would be best to lower the factory settings. I may not have a clue what im talking about or even if what I just said makes sense which is why im asking for help.. so any other opinions on if it would be a good idea or not to run at a lower temp, would be great.. and i may have found the switch I was looing for, is it closer to the firewall? if not, ill look for the empty thread hole, but im pretty sure its not controled by the ecm.
Thanks guys.
Oh and is this how it works? coolant temp sensor on the intake sends a signal to the switch on the head, which sends a signal to the relay on the firewall which grounds the fan? seems like a lot of work to turn on a fan.
Switch in head closes when set point is reached; switch operates relay coil; relay contacts send power to fan.
Kind of extremely no-brainer simple, really. Kind of on down there at a level where even someone as dumb as I can understand it.
Not sure anything about "access", or even excess, fuel, in any of this. This is mostly about cooling the engine. Since a 50/50 mix of antifreeze and water under 15psi of pressure doesn't boil until it reaches about 270° or so, and cast iron doesn't melt until well in excess of that, the factory's temp settings seem kind of reasonable. Cars last hundreds of thousands of miles with that setup. Doesn't seem to be an issue.
The sensor in the driver's side head operates the gauge. That's it, nothing else.
Your car worked fine when it was new. If it's broken now, you can fix it. If it works the way it was built, and you use it the same way that it was built for (driving around on streets), then that's something that there's just not alot of point in messing with.
You're right, it's not controlled by the ECM. Only the switch, and the AC (since the AC needs to move heat, and therefore needs air to be flowing, regardless of the engine temp).
__________________ Numquam ponenda est pluralitas sine necessitate. — William of Ockham, from Quaestiones et decisiones in quattuor libros Sententiarum Petri Lombardi
Roughly paraphrased into modern English, and applied to figuring out what's wrong with your car:
The simplest explanation that fits all the facts is probably the right one.
To tell the ECM what temp the coolant is, so it can adjust the fuel flow (in minor ammounts) as well as spark, and it will know when to go in and out of closed/open loop from there. It's much more accurate than the gauge sender (since the sender is just a ground resistor).
Single green wire, slide/blade terminal, left side head between #1 & #3 spark plugs = temp gauge sensor
Single green wire, round pin-looking terminal, right side head between #8 & #6 spark plugs = fan switch
__________________ Numquam ponenda est pluralitas sine necessitate. — William of Ockham, from Quaestiones et decisiones in quattuor libros Sententiarum Petri Lombardi
Roughly paraphrased into modern English, and applied to figuring out what's wrong with your car:
The simplest explanation that fits all the facts is probably the right one.
I think you all need to do just a bit more research, or maybe I'm wrong. I believe the sensor in the passenger side head is for an overheat condition, a failsafe. The ECM actually controls the fan from the two wire sensor in the intake. That is why that sensor in the head is such a high temp unit. And the head runs a bit hotter than the overall engine somewhat. I put a lower temp (200 degree) sensor in that position and the fans came on before the thermostat even opened. If you have no sensor in the passenger side head you can hook a switch or sensor into the fan circuit at the AC high pressure switch that also turns the fan on.
In search of cheap power! 
B4 with a new 235 switch installed on pass side, the fan never kicked in unless a/c was on, ok maybe twice but there were plenty times when were in 250's & no fan. so maybe you can see why I'm using a lower temp switch that works 95% of the time... those double fans reallly sound good at this point lol. I replaced the sensor on driver's side B4 , but no change to fan control. What does the sensor on the drivers side feed? 
